Serial quantitation of BCR-ABL IntroductionReverse-transcription real-time quantitative polymerase chain reaction (RQ-PCR) is used routinely to quantify levels of BCR-ABL mRNA in peripheral blood and bone marrow samples from chronic myelogenous leukemia (CML) patients undergoing therapy. The technique can accurately determine response to treatment and is particularly valuable for patients who have achieved a complete cytogenetic response. The National Comprehensive Cancer Network (NCCN) 1 and the European LeukemiaNet (ELN) 2 recommend similar monitoring schedules for patients treated with imatinib and the ELN defines an optimal response as the attainment of a major molecular response (MMR) after 18 months of therapy. Monitoring of BCR-ABL mRNA levels is also useful for gauging therapeutic response for patients with Philadelphia chromosomepositive acute lymphoblastic leukemia (Ph ϩ ALL). The CML meeting at the National Institutes of Health in Bethesda in October 2005 made several recommendations for the harmonization of minimal residual disease (MRD) assessment and proposed an international scale (IS) for BCR-ABL RQ-PCR measurements. 8 Importantly, the IS is essentially identical to that used in the International Randomized Study of Interferon and STI571 (IRIS) study, 9 with the IRIS standardized baseline defined as 100% BCR-ABL IS and MMR (3-log reduction relative to the standardized baseline) defined as 0.1% BCR-ABL IS . The original standards used for the IRIS trial are no longer available, however traceability to the IRIS scale is provided by the extensive quality control data generated by the Adelaide laboratory over a period of several years. 10,11 To enable testing centers to gain access to the IS, the Adelaide laboratory initiated a process to develop and validate laboratoryspecific conversion factors (CFs) that can be used to convert local values to IS values. 11 The strength of this approach is that testing centers can continue to use their existing assay conditions and continue to express results according to local preferences in addition to expressing results on the IS. The concept of the IS is analogous to established procedures for other quantitative assays, for example the International Normalized Ratio (INR) for prothrombin time. 12 Many laboratories with validated CFs have established themselves as national or regional reference laboratories and are in the process of propagating CFs to local centers. 13 While this process has generally worked well, it is apparent that the establishment of CFs is time-consuming, complex, expensive, and open to only a limited number of laboratories at any given time. Furthermore, it is unclear how frequently any individual CF will need to be revalidated. We sought therefore to develop an alternative means for testing laboratories to access the IS by developing calibrated, accredited primary reference reagents for BCR-ABL RQ-PCR analysis. StrategyIdeally, the formulation for primary reference reagents should be as close as possible to the usual analyte, should cove...

Clonal proliferation in myeloproliferative neoplasms (MPN) is driven by somatic mutations in JAK2, CALR or MPL, but the contribution of inherited factors is poorly characterized. Using a three-stage genome-wide association study of 3,437 MPN cases and 10,083 controls, we identify two SNPs with genome-wide significance in JAK2V617F-negative MPN: rs12339666 (JAK2; meta-analysis P=1.27 × 10−10) and rs2201862 (MECOM; meta-analysis P=1.96 × 10−9). Two additional SNPs, rs2736100 (TERT) and rs9376092 (HBS1L/MYB), achieve genome-wide significance when including JAK2V617F-positive cases. rs9376092 has a stronger effect in JAK2V617F-negative cases with CALR and/or MPL mutations (Breslow–Day P=4.5 × 10−7), whereas in JAK2V617F-positive cases rs9376092 associates with essential thrombocythemia (ET) rather than polycythemia vera (allelic χ2 P=7.3 × 10−7). Reduced MYB expression, previously linked to development of an ET-like disease in model systems, associates with rs9376092 in normal myeloid cells. These findings demonstrate that multiple germline variants predispose to MPN and link constitutional differences in MYB expression to disease phenotype.

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